I mean if you have the event Magikarp with Hydro Pump or a hacked Magikarp with any water-type moves like Surf. I think so since it would make sense but without event or PowerSaves it's impossible to get a legit water-type move on Magikarp. Would it get STAB? Just wondering
Here is the event Magikarp that i'm talking about:
Yes there is no reason it why it shouldn't work, even if it is hacked; the move gets STAB if it's type is the same as the user's.
Yes, it does. There is an event magikarp with hydro pump to ensure it too.